Participants chopped off fingers, licked plated and became chefs…The dieting study that started it all.
A booming area of research right now (and one of my favourites) is the metabolic effects of dieting, and strategies to mitigate such responses. As most of you will be aware, adaptive thermogenesis refers to the decrease in resting metabolic rate during dieting that isn’t explained by loss of body mass (1-3). This of course is one of the reasons people run into weight loss plateaus despite low caloric intake, and why rapid weight regain is often observed early in the post-diet period when “normal” eating is restored. For the last couple of years as intermittent dieting strategies like refeeds and diet breaks made their way onto the scene, it has been common for coaches to tell their athletes that they don’t “deserve” higher calorie periods unless they are very lean (recently I saw one coach on IG say that no one needs a refeed unless they’ve got glute striations).
One of my favourite studies of all time is the 1944 Minnesota Starvation Experiment. (4) In this trial, it was clear that adaptive thermogenesis occurs after only three days of dieting on approximately 1600 calories, with the greatest suppression of resting metabolic rate occurring in the first two weeks of the study.
This gives support to refeeds and diet breaks (strategies that can potentially mitigate reductions in resting metabolic rate) being implemented early on in the diet phase. However, we still don’t know how long refeeds should last, how frequent they should be, or how many calories should be consumed. In the Minnesota Starvation study, resting metabolic rate after three weeks of dieting was completely restored after seven days of refeeding (however this was eating more than a bodybuilder would typically eat during a maintenance calorie refeed). This finding does tell us that returning to energy balance (at least enough calories to maintain weight) does provide restoration of suppressed resting metabolic rate but given that it’s more common for bodybuilders and physique athletes to refeed on less calories, and typically only last 24-48 hours, it’s unknown if this is a potent enough stimulus to trigger metabolic normalisation.
While there is evidence for refeeds and diet breaks to be implemented early in the diet phase, there is also a solid rationale for less frequent use of these strategies early on, and more frequent use as the individual approaches leaner levels of composition. (5-6) It’s quite well known that the adaptive responses to dieting become more pronounced as an individual loses more body weight and fat, or the longer time spent in a caloric deficit. This is evidenced by greater losses of lean tissues, impairments to anabolic hormone profiles, greater irritability, and reductions in mood and vigour. Considering diet breaks and refeeds are proposed to mitigate such responses, it’s feasible that a leaner individual may gain more benefits from these strategies than an individual with higher body fat. If so, this would have practical application as coaches and athletes would be able to apply intermittent refeeds or diet breaks more frequently as body fat is reduced, with greater positive affect. We may have a study in the works to test this theory….stay tuned.
I’m going to leave you with a few of the less spoken about findings from the Minnesota study, because quite simply they are remarkable. Most of us would be aware of the decline in physical energy, mood and motivation that accompanies significant weight loss. In the Minnesota study, researchers reported participants being aggressive in the diet kitchen, annoyed by each other’s voices, and an increase in strange eating habits (With one participant coddling the food like it was a baby, and others playing with it).
Plate licking was common place, participants diluted potatoes with water and held bites in their mouth for a long time without swallowing in attempts to extend mealtime and or feel fuller. Some men were observed staying up until 5AM studying cookbooks, with some becoming chefs after the study.
Many started smoking to stave off hunger, and others chewed up to 30 pieces of gum a day until the researchers banned them! Researchers reported budding romances collapsing, decreases in sexual desire, and men preferring solitary trips to the movies instead of social events. While one man was chopping wood, he amputated three fingers. When asked about the “accident” he responded, “I am not ready to say I did it on purpose. I am not ready to say I didn’t”. Have you ever chopped off some fingers to get out of dieting?
I’m sure you can find humour in these case reports (as do I), yet it’s important to note that this study was completely ground-breaking in the way it first documented the mental, physical and social effects of food restriction. Before this paper, these responses were relatively unknown and undiscussed. 75 years later…the rapid, strange and alarming changes in physiology and psychology due to dieting is still being studied, with strategies targeted at reducing the severity of such changes now at the forefront of research efforts.
The People Punching Peacock
- M Rosenbaum, Adaptive thermogenesis in humans. International journal of obesity (2005) 34 Suppl 1(1):S47-55 · October 2010
- Leibel R, Rosenbaum M, Hirsch J. Changes in energy expenditure resulting from altered body weight. N Eng J Med. 1995; 332:621–28.
- Weigle D, Sande K, Iverius P, Monsen E, Brunzell J. Weight loss leads to a marked decrease in nonresting energy expenditure in ambulatory human subjects. Metabolism. 1988; 37:930–36. [PubMed: 3173112]
- “Men Starve in Minnesota.” Life 19, 5 (July 30, 1945): 43–46. https://books.google.com.au/books?id=z0kEAAAAMBAJ&lpg=PP1&pg=PA43&redir_esc=y&hl=en#v=onepage&q&f=false
- Peos et al, Intermittent Dieting: Theoretical Considerations for the Athlete. Sports 2019, 7, 22; doi:10.3390/sports7010022
- Peos et al. Continuous versus intermittent moderate energy restriction for increased fat mass loss and fat free mass retention in adult athletes: Protocol for a randomised controlled trial – The ICECAP trial (Intermittent versus Continuous Energy restriction Compared in an Athlete Population), BMJ Open Sport & Exercise Medicine 4(1):e000423 · October 2018